Vongola Bureau of Investigation
by PerezLycan
Summary: Tsuna has took his first steps to being a Mafioso and leader for his Family. There is one in particular he can't define his relationship with. His other mist guardian. Why? Were they friends or only allies? They have transferred to a new division and entered a life of crime. They will enter the nightmare belly of the underworld. Boss and Nagi will only have eachother as partners.
1. Chapter 1

_Prologue_

 _1_

Knock, knock.

"O-Oh, come in?!"

She stepped inside. His _other_ mist guardian scooted in. That's how she was referred to. He didn't appreciate that. She was Chrome and she was family. Period.

"Chrome, what is it?" Boss always had time for his friends.

"N-No, it's another file from the Ninth." She saw his eyes drop.

"Oh. Leave it on my desk."

"Yes, Boss."

"You know Chrome, you can call me Tsuna, if you want."

"I do know... Thank you, Boss."

She pretended she didn't hear him sigh as she closed the door.

* * *

It was late, a hot mug of coffee was on his desk when he walked back into his office. He wasn't puzzled by it. He smiled reading the note under it.

 _I'm going home for the day, Boss. Don't work yourself to death. We also have school in the morning._

"I won't Chrome."

He sat down and sipped on his coffee. He didn't know if she cared for him or was doing her job as his mist guardian. "Two spoons of cream and no sugar, how does she know." A light chuckle.

That curved downward.

He frowned. She knew him so well, but he knew nothing about her. Why was that?

He ruffled his hair. "Stop it. That's how Chrome is." He whined to himself

He wanted to get to know her, at the very least. He was going to be a Mafia boss, already training.

The Ninth was kind and gentle to all his guardians, to everyone honestly. 'His guardians all give him that warmth of family. With Chrome it's?'" He sighed out, finishing his thoughts with words.

The next day, Tsuna yawned as he met up with his family. They all began to walk to Namimori High.

The only one missing was Chrome, but they were on their way to her train stop. They always looked out for eachother. Hibari didn't crowd with them, but he lingered occasionally. Mukuro always knew how his 'Nakama' were doing. They all awaited in front of the train, as the door open.

In that moment of forever, _s_ _he smiled._

Chrome stepped out and stopped in front of her family. Mafia or a real one?

Tsuna was in the middle.

"Hello Boss. Good morning, everyone."

Boss took a step forward with a casual smile. "Hey Chro-" He slipped and fell on the train tracks. Thank God it just left and one wasn't on the way. 'Why is it always like this? I can't even talk to her...'

"Are you ok?" She was giving her hand, as she would with any body part.

She was bending down offering herself, he didn't know if it was purely for help.

Duty? Friendship? M-Maybe a bit more? 'No! No, don't over think it.'

"C-Chrome! Y-Yea, sorry." He reached out. He reached out to her.

"Boss, You shouldn't need to apologize to your guardian." She whispered naturally. Tsuna stood, he was about to thank her until he heard that. "O-oh."

And they walked to school.


	2. Chapter 2

Chapter 2

A new school?

"EEEEEEHH?" Tsuna cringed as they reached their school. Yamamoto laughed along with Ryohei's exciment.

"I wonder what they are building?" Kyoko had her finger to her lips in thought.

"A new school." Chrome informed. Hibari rose an eyebrow, who was invading his territory.

Tsuna twisted his head timidly to her. "Huh? Chrome how do you know?"

"Reborn asked me to fill out the paperwork."

"Eeeeeh!?" 'Reborn is still up to his shenanigans... Wait! Why is Chrome helping him!'

"I thought it was a good idea." She smiled at him. How did she answer a question he only thought about?

He dropped his cringed shoulders and sighed out. "How much is it gonna cost?"

"Don't worry, I handled that as well Boss. I know how you struggle with math."

'Now she's just messing with me.' He droped his head in self pity. He heard a simple giggle escape her lips. She secretly nodded at him. They stared for a moment. She tucked a strand behind her eye, letting her see Boss. Her light laughter stopped but the smile reminded. She blinked the moment away. His eyes didn't blink as his cheeks grew red. He mentally slapped himself and straightened up. 'Ch-Chrome can be really cute when she teases. I think that's the first time she has done that. Is she getting more comfortable around us? Me?'

"You're not focused!" A giant green ten ton hammer fell from the sky. Tsuna's eyes bulged out wide as he was buried down to his waist in the sidewalk.

"Reborn!" Tsuna yelled at the small baby that landed on Yamamoto. "Why did you build a school on the opposite side of ours!" Not even complaining for the almost burial.

Reborn's eyes shadowed. "There isn't enough room for two schools on this street." The dynamite in one hand the lighter in the other.

"R-Reborn! Don't blow up our school!"

He paused with a baby blank expression. "Nani? You and your guardians have been transferred to mine."

"Eeeeh? What, when?" He paused and made eye contact with her. She simply waved. 'I-I physically can't be angry with her... She's being really cute.' He mentally cringed at his dame nature.

"Chrome-"

"Filled out the transfer papers, I know." He sighed out, but smiled. It was feeling like maybe they were friends.

"Don't get smart with me." He lept off Yamamoto and loomed over Tsuna.

"Hiiieee!"

* * *

Chrome took a small skip a head of them as they reached a massive silver gate blocking site and access to the construction site. She turned and faced them all. Her hands were clasped behind her back as she leaned forward with a smile. "I thought this could be a new beginning for all of us."

Everyone agreed to her thoughtfull gesture. Tsuna was the only one who couldn't. 'H-Has Chrome always been this beautiful...' His eyes wided at his very own, quickly beating heart. 'Wh-What? No I can't be!- She likes Mukuro... She even said so during the battle for the watches, besides I never got Kyoko-chan to really notice me. What shot do I have with Chrome. I mean only if I liked her! Which I dont!' Who you trying to convince, Tsuna? Yourself or us...

"What do you think, Boss?" She was so nervous being honest with them all. It was a big step for her... Yet Boss, the one who unknowingly helped her have the courage, was the only one who hadn't replied. 'Did I go too far with the teasing? Should I have asked for his approval first?'

Her words snapped Tsuna out of his confused daze. "I-I think it's great Chrome! You really thought about us, huh?" He had a toothy smile. He didn't know if he liked her, but was overjoyed. She did consider them family.

She quickly grew embarrassed at the praise. She still wasn't used to that. "Th-Thank you, Boss."

Tsuna is just dense. "Your welcome!" Not realizing how he emotionally affected her as well.


	3. Chapter 3

**Hey everyone. Hope u enjoyed the nice small fluff intro. This gonna be my newest Tsuna Chrome Story. This is kind of the first real chapter. This story is a slight romance but also mafia crime and drama. Shoot outs and heavy themes, eventually M. It's gonna get intense bruh. Not as fluffy as the intro.**

Chapter 3

Vongola officers.

The huge metal gates opened behind Chrome. One of their closest friends came out. Constriction work could be seen behind her as she walked to them. "Hello everyone."

"Yuni!" Tsuna smiled and ran up to his old friend from the future.

Chrome close behind, followed by Gokudera and the rest.

Chrome eyed the gift in her hands. 'For Boss?'

"What are you doing here?" Boss asked, shocked at her appearance from the developing school. Chrome was caught off gaurd for a sec, not because of the question, but after he did ask it, he turned to Chrome, asking with his eyes. "Did Chrome tell you about all this?"

Chrome was beginning to shift her feet nervously. 'B-Boss's hyper intuition caught on fast.'

Yuni replied with her usual happy nature. Only a little surprised he guessed right. "We have been talking about the school for a while actually. Alot of us are going to attend, it's gonna be fun, when it's finished."

Tsuna smiled and then turned to Chrome. "You put alot of thought into this huh, Chrome?"

"I did." She kept her posture and words straight, but was panicking inside. She was going noticed for her self, not as a vessel. "But it's not ready yet. A week at most. I hope that's okay with you Boss."

He smiled. "Chrome, you're really amazing."

She hid her mental squirm.

Yuni glanced at the two. She presented Tsuna with a gift. "Here this is for you. It's from me and Byakuran. It was your treasure in a parallel world."

It was wrapped in a white silk, but Tsuna was able to make out the shape. "A pistol?" He reached out and unwrapped it, then held the handle. "Yuni... why would this be my treasure?" 'A different me... killed...'

She frowned. It was better if he didn't know about the mercenary version of Tsuna. "It was your W _hite owl_."

"White owl?" He stared at it. In his hand was an obsidian desert eagle with twenty-seven etched in a skyflame engraving on the handle. It was nothing like a white owl. He was about to ask why it was named that.

"Like my owl, Boss." Chrome's finger tips traced over the letters, also grazing his fingers. His eyes landed on hers. She had a small smile, staring at his new gift.

'I guess it doesn't really matter what the parallel version of me did with this... Chrome likes it. I'll keep it.'

"Ah, you're right Chrome." He then turned to Yuni. "Thanks Yuni, I'll take extra good care of it. But I don't think I'll use it." As he naturally tucked it behind his back. 'Too familiar.'

"You might have too, Dame-Tsuna. You have already been assigned a case. Don't think you can get out of your duties as a Mafioso." Reborn scolded. He landed on Tsuna's shoulder and handed him a folder.

"Ara?" He opened the file. Was someone from his family in trouble? But most of them where right next to him. He frowned seeing a photograph and documents in the folder. "M.M."

Chrome perked up at that.

"She's gone rouge? Even leaving Mukuro's gang. Reborn why woud I have to investigate?"

His eyes, the cold marbles. "She ran off with sensitive documents and a handful of our funds."

Tsuna grew a bigger frown. M.M. was... He sighed he didn't know her to well. He knew she was greedy, but never imagined her leaving Mukuro. 'Even if I don't know her well, it's not like I want something bad to happen. What was she thinking stealing from the Vongola.

"Um, Chrome would you know why..." He hesitated staring into her confused eye. Was she also recently finding out? "...She would-" But he didn't finish the sentence. Chrome's eye held guilt for not knowing, and not able to assist her Boss. The liquid shimmering over her eye spoke of concern for M.M.

"B-Boss, maybe we should speak in private?" She didn't feel comfortable with people prying their eyes to this sensitive matter.

"Chrome you have also been assigned to this."

She blinked. "Eh? Me, are you sure."

Reborn smirked. He nodded and pulled out an official document sighed by the Ninth. "As of Today, both you and Tsuna are now Vongola officers and partners."

He gave a document to both Tsuna and Chrome, along with a crest of the Vongola's insignia to be worn on duty. "You both have skills that the Ninth believes will be valuable to solving crimes in the mafia world. The Vindice no longer affiliate themselves with mafia law and a new branch in the Vongola was formed. The Vongola Bureau of Investigation."

Boss and Chrome glanced at eachother. Both with the same anxiety. He glanced back at Reborn. "Only us two? What about everyone else?"

Reborn nodded. "They have all been transferred to different sections in the Vongola." Reborn informed handing each a document with instructions.

"The explosives division. I won't the Tenth down!"

"Contracts, sounds fun!" Yamamoto laughed. Tsuna cringed. 'He is going to be a hitman...'

Ryohei was going to be a close quarter combat instructor. Hibari already created the foundation. Lambo was too young, and Mukuro didn't take orders from the Vongola.

"Do not take these responsibilities lightly. The mafia is a cruel world. When this school is finished, it will be your only connection to your youth. Tsuna, Chrome head back to your office and begin to investigate M.M."

"Ara, so soon? But where do we even start?"

"I'm not going to baby sit you anymore Dame-Tsuna. The Ninth believes you can accomplish this... with your partner." He glanced at Chrome then back at Tsuna before he left in is leon-air ballon.

Tsuna and Chrome fidgeted, not knowing knowing where to go from here. The others were slowly departing, headed to their newly assigned job. "Let's all see eachother when school starts, guys." Yamamoto laughed, with his hands behind his head. Gokudera proclaimed he would be better at his job than the baseball freak.

They were left alone. Chrome, Boss, and Yuni. "I hope your friend is ok, Chrome." Yuni also looked worried.

She stiffened slightly. "S-She's not really my friend, but."

Tsuna stared at the crest Reborn had given him. He glanced at the purple orb that was thinking of M.M. "Don't worry, we'll figure it out. Together, Chrome."


	4. Chapter 4

Chapter 4

The scarlet runner

Tsuna and Chrome decided it was best to head back to the office they had been working in after school.

The subway was railing along the city-bridge tracks. "What's the Ninth and Reborn thinking?" Tsuna mumbled, sitting next to Chrome.

Chrome was still looking over the files Reborn gave them. "It's true, we have no formal training."

Tsuna leaned his head back against the window. "Yea, I don't know how we should even begin. What's up with the pistol and badge. It feels too serious." He cringed. Not able to grasp the reality slapped across his face. A Mafia officer, was that even a real occupation?

She nodded. "Yes, but I believe you were assigned this, because of your hyper intuition."

Tsuna glanced to his side. Her eye was still focused on the picture of M.M. "Maybe, and you're pretty good at figuring things out."

She rose her eye. Blink. She focused more on the conversation for a second. "You think so? I believed, it was for my illusions."

'That's another good reason.'

* * *

They were in his office. Now suspiciously organized with her desk and computer.

It was facing a window on his right. Tsuna was the opposite. His desk was in front of a window behind him, as he faced the door to his office.

It had been about half an hour since they entered with all the files they could find on M.M. Unfortunately there was little to go by.

This building was the H.Q. for the Vongola in Namimori. The underground facilities were under construction.

They worked in a skyscraper, with his floor on the top. An office for each of his family members. Chrome didn't need hers anymore.

"Ken and Chikusa aren't picking up." She slowly tore the phone from her ear.

Tsuna nodded to her words. He was reading an article on his computer desktop about M.M. "She owes alot of money throughout Italy. No wonder she has been staying around here."

Chrome stared at her phone. Why weren't they answering? 'Maybe Mukuro knows.'

Tsuna shifted his eyes to her as she faced the window and city. She was mentally debating with herself. 'Of course Mukuro knows something...' He couldn't ask her though. He didn't understand the dynamic of the Kokuyo gang. Did Chrome, herself?

Tsuna ruffled his hair. 'How are we supposed to solve crimes, when we are only third years in highschool. I can't even solve normal problems for my family.'

"Boss, we should check Kokuyo land. Even if they aren't their anymore." She stood from her desk.

Tsuna glanced at her. "Why would you say they left, Chrome?" He stood, eyeing her assumption.

"It may have been their plan."

He gasped.

* * *

Boss and Chrome stared at the roof and windows. The main building of Kokuyo land was a disaster.

"It's a little more chilly around here, ne?" Tsuna mumbled.

Chrome nodded.

They had found two mafia officer hand books slung on the doorknob of Tsuna's office.

It laid out a set of rules and regulations for them as officers.

Following protocol. They were wearing mafia attire.

Boss had a black suit with an white dress shirt. The crest of Vongola was over his heart. His Desert Eagle, the white owl, was in a holster around his belt.

Chrome was the same with a skirt, thigh high boots and stockings. A glock was strapped to her inner thigh.

"Come on let's see what they left." Chrome mumbled. Both her and Tsuna had been reading the book. He still had no idea what they were doing, but Chrome seemed to understand the jist of this. 'No, that's not it. She's worried for them. What do we do if they did betray us?'

Ruble skipped. They kicked some entering the building. "It looks deserted, but it always has." Tsuna sighed, it was probably a dead end. He followed her up some stairs.

"Her room was next to mine." She mumbled.

Tsuna glared down. Her words, case related or personal?

"Is that so?"

She nodded taking the last step in front.

Tsuna opened the door for her. She was mentally debating if she should or shouldn't.

"She didn't like you entering?"

She nodded again.

Boss and her, scavenged for clues, but her room was cleared out in a hurry. 'We are getting no where fast.'

"Sorry Boss, I don't think we will find anything here." Chrome mumbled after inspecting all her drawers and the closet.

"That's what bothers me." Tsuna replied.

"Ara?"

"I don't think M.M. was the one who cleared this place out."

"You don't?"

Tsuna shook his head, glancing at the empty, trashed room. "Look, crumbs of sweets are all over the floor. Alot of expense looking clothes were left behind, and it's folded neatly in the drawers. M.M. loves fashion she wouldn't have left it."

"Ken and Chikusa were here."

Tsuna nodded. That led him to believe something else. "They might of came looking for her."

"...So it wasn't the Kokuyo gangs plan." A little bit of hope.

Tsuna shook his head. "We can't say that for sure. Maybe they came to pick up things for her, or maybe she stole from them too and they are looking for her too."

Tsuna frowned more questions than answers.

"Boss, it might be a chase between them and us for M.M."

He nodded at her. Boss rubbed his chin. He knew one thing was for sure, but he didn't know, "How does Mukuro fit into all this?"


End file.
